Method for continuously producing vulcanized fiber



June l5, 1942- Y G. E. LANDT I 2,286,968

METHOD FOR CONTINUOUSLY PRODUGING VULCANIZD FIBER 'w HIHUI Il ll I t w I'u G v ,uli

' June 16,- 1942. 2,286,968

METHOD FoR'coNTINUoUsLY PRODUCING vuLcANIzED FIBER l G. E. LAND-r Filed Feb. 1, 1941 2 Sheets-$11991'l 2 Maw fwd tion of vulcanized fiber.v

Patented June 16, 1942 -METHOD FOR CONTINUOUSLY PRODUCING i l VULCANIZED FIBER Gustave E. Landt; Norristown, Pa., assignor to Continental-Diamond Fibre Company, Newark, Del., a corporation of Delaware Application February l, 1941, Serial No. 377,038

6 Claims.

This invention relates to a method for continuously producing parchmentized or vulcanized ber, and to the resulting product.

It has been noted that the cellulose molecule is composed of unit cells which are assembled in long chains of fifty to sixty in length, the chains being associated in parallel combination to produce a cellulose micella. Such chain molecules further combine to produce the elementary ber structures which characterize cellulose. In the manufacture of parchmentized or vulcanized fiber, consideration of the micellar character of cellulose is of vital importance. The standard operations in producing vulcanized ber 4are to pass a pluraliy of sheets of paper l,through a bath of a suitable chemical such as zinc chloride and to combine the sheets thus saturated into a composite strip. The chemical is subsequently leached out and the strip dried. The chemical treatment of the sheets results in breaking down the ber structure to form a mat of cellulose micellae. The surfaces of individual cellulose bers are progressively transformed and the chemical action is relatively more or less complete depending on the depth of the ber structure to which the chemical permeates. Each fiber then readily coalesces with other bers, producing a relatively continuous cellulose structure in the strip. After leaching out the chemical. the continuity of the cellulose structure is more or less preserved, depending on the intensity of the action of the chemical and on the characteristics of the drying operation in eliminating moisture. A single sheet of parchmentized fiber is produced by the same general method except that a plurality of sheets are not superposed to form a composite sheet as is the case in the produc- Generally speaking, if moisture is eliminated slowly and gently,.the sheet is exceedingly tough; whereas, if it is removed rapidly, as by the ordinary drying process against steel drums or other artificially heated equipment, it is relatively brittle.

In the manufacture of these sheets of vulcanized ber, say from .005" to .125" thick, the strip, immediately after its formation, passes in an endless web through subsequent leaching and puring baths and to driers of the type usually employed in paper machines.` As previously carrled out, the strip in its passage through the various baths is guided over rollers through.' which the strip is threaded to keep the same running smoothly on the production line. Ob-

viously, drawing a strip which is in a large measure in theform of a gel and, as a matter of fact, in the early stages of its formation has -a semijelly-like characteristic, places strain thereon. In the drying end, the fiber must necessarily move slowly due to its high density. Also, due to its high density, there is a decided tendency of the sheet to dry unevenly and, therefore, to cockle. As a result, at the drying end .it has been considered important to keep the web of drying liber` pulled down tightly against the drying cylindersand to exert considerable tension on the ber at the calender stacks which are located at the discharge end of the drying section.

I have discovered that the tensioning of a sheet in the peptonizing (chemical treatment), leaching, puring, and drying operations has, due

to the micellar structure of the ber, been a principal factor in affecting the characteristics of the fiber sheet. Stresses set up as the web of ber is pulled over rolls,.wound on reels, transported from tank to tank, and nally dragged over the driers, result in the development of internal strains and finally in the production of a material in which the unitary structures of the long chain molecules or micellae have been strained to align their axes in a direction parallel to the direction of travel. As a consequence, the finished material lacks uniformity with respect to its cross machine and machine direction properties and has a decided tendency to curl and warp when subjected to moisture.

It, -furthermore, has a tendency to delaminate A cates that internal strains are being set up in the strip and'this indication is further strengthened by the behavior of the fiber in its subsequent lift. It tends to become brittle and its usefulness is thereby impaired. Under the inuence of a change in humidity, it tends to twist and curl. A sample of such fiber, when nished on the machine, if floated flat on the surface of considerable water will curl into a tight cylinder, whereas a strip of the same ber in which the tensions have been released will only become moderately concave. These tests have, likewise, indicated that the critical stages in handling are during the peptonizing and nal drying of the ber, a less critical stage being during the leaching and puring.

In accordance with my invention, the ber strip from the time that it leaves the making rolls until the time it is completed (throughout the nal peptonizing, leaching, puring, and drying operations) is freed from strains. While benecial results are obtainable by relieving strains at one or more of these points, optimum results are possible only by complete relief of strains at all points thereof. Essentially, the invention resides in the application of the principle of supporting the treated strip through the processes of peptonizing, purifying, and drying the same as distinguished from drawing or forcibly pulling it during these operations. To this end, a continuous processing machine embodying the principles of my invention must embody a means for supporting the treated web during the time interval in which the peptonizing action of the employed chemical is permitted to take place; a means for floating the peptonized paper through the leaching operation to permit removal of.'V the zinc chloride; and a means for drying the ynished strip to again support rather than draw the web through the drying device. A machine of `this character is illustrated in the accompanying drawings where- 1n,

Fig. 1 is a semi-diagrammatic view showing the wet end of a continuous ber machine for carrying out my method; Y

Fig. 1a is a semi-diagrammatic view of the dry end thereof;

Fig. 2 is an enlarged detail sectional view illustrating one method of supporting the ber strip during the leaching and puring operations; and Fig. 3 is an enlarged detail view illustrating a preferred method of eliminating strains during the drying operation.

Referring now more particularly to the drawings, the forming end of the machine may be substantially that of the usual ber machine, comprising a chemical vat I0 which may, for example, contain a solution of zinc chloride, and in which suitable guiding means, indicated at I I, are provided for guiding a plurality of paper sheets 4I 2 into and through the vat for treatment by the solution therein. Adjacent one end of the vat are heated forming rolls I3 by means of which the combined sheets I2 are caused to adhere to one another in theform of a single strip I4. In accordance with my invention, the strip as discharged from the forming rolls is lplaced upon a series of conveyers I5, I6, and I'I, theseconveyers being of a suitable length to enable the proper peptonizing action prior to introduction of the strip to leaching vats I8. The conveyers I6 and I1 are driven at the same speed as the surface of the roller series, it will be obvious that any such action will impart considerable strain to the strip which, at that time, is in a semi-jelly-like condition. Likewise, in the ordinary machines, and preceding the reel just mentioned, there are usually a number of rolls about which the strip is threaded and over which it is drawn by the reel, and this again imparts considerable strain to the material. In place of the bath of zinc chloride, other peptonizing or parchmentizing baths may be used, for example, a bath of sulphuric acid, calcium thiocyanate, or the like.

By my method, when the strip passes from the conveyer I'I, it is led downwardly into the leaching vat, or vats, and floated therethrough with the least possible longitudinal strain thereon. In the present instance the leaching vats, two in number, have been illustrated as provided with rotating reels I9, the peripheries 20 of which are formed by spaced longitudinally extending rods 20. These reels are advanced periodically through a Geneva movement comprising teeth 2I carried by one of the heads 22 of the reel andha'ving associated therewith a rotating pulley 23 provided with a single tooth. Above the reel is arranged arotating drum 24, the surface speed of which is the same as that of conveyers I6 and I1 and over which the ber strip is trained. It will be noted that in the-rst of the vats I8 the ber strip is shown as passing about a single roller 25 to which it is fed by gravity from the conveyer I1 and rotation of this drum merely serves to elevate the strip to a point above the associated reel. Since conveyers I6, l1 and drum 24 have the same surface speed and the strip moves by gravity to the roller 25, the only strain on the strip at this point is that represented by the weight of the ber strip between roller 25 and the drum 24, and in fact less than this since the submerged portion of the strip speed of forming rolls I3y with the result that no strain is placed on the sheet during the peptonizing stage of the process.. These conveyers replace a series of rollers used in the ordinary machine and over which the strip is drawn through the will tend to oat.

The ber drops freely from the drum 24 between the bars 20 of the reel and is thus formed in festoons which are progressively fed around the reel to the point where they are freely taken oiI for passage to the drum 24 of the succeeding vat. Instead of drawing the ber free of support to the upper surface of the drum 24, there may be provided a roller ramp such as shown at 28 over which the ber may pass. It will be noted that, since the specic gravities of the ber and the water in the leaching and puring vats will be substantially the same, the ber in most cases being the lighter, the ber sheets carried by the reel will be floated therethrough to the point of discharge.

The drier part of the machine comprises a series of drier drums about which the strip is trained, these drums comprising primary drying drums 21, intermediate drying drums. 28, and final drying drums 29. The primary drying drums 2'I may be driven at the same surface speed as the drums 24 and conveyers I5, I6 and I'I. It is obvious that the ber strip will shrink during the drying process, but I have found that the primary drying action on drums 2'I does not cause any appreciable shrinkage. At the point where shrinkage starts, the drums 28 are employed, these drums being divided into groups of two drums each, as more clearly shown in Figure 3. Each group has a controller generally designated at 30 including a rheostat 3| controlling a motor 32. This rheostat is controlled by an oscillatory arm 33 which is suitably connected with the rheostat as, for example, by the segment and pinion construction illustrated at 34. The

speed of the motor to compensate for the change in tension which is kept at the lowest feasible point. With the ber lightly tensioned, the dryling operation more nearly simulates air drying. The similarity to air drying conditions is further increased by providing between adjacent runs of the fiber strip air pipes 3B supplying a blast of air under pressure against the surfaces of the strip. The drums 28 are made suicient in number so that at the end of this series the fiber strip has dried to a point where further shrinkage will not occur, and the nal drying drums 29 need'not be equipped with the automatic controls just described.

Due to the fact that the strip has not been v tensioned during the peptonizing, leaching, and puring operations, there is little or no tendency of the strip-to cockie. The air blast delivered by pipes 36 further reduces the tendency to cockle, thus enabling the same to be passed through the drying section under tension just sufiicient to cause its progress therethrough.

The following tables give comparisons of relative strengths and ply adhesions in identical ber made under the old method and under my method as above outlined:

Tensile strength-New method In that portion of the table dealing with the new process the points A, B, C, and D represent'the points designated upon the machine at which the samples were taken therefrom and samples made in accordance with the old, method were taken from corresponding points in the apparatus employed in carrying outthe same. It'will be noted that there is a distinct improvement in the ratio of tensile strengths in the machine and cross-machine directions at each of the stages of treatment of the material, the aggregate being an increase in this ratio from 35.5% to 58.3%.

It will also be noted that while in both the one or more of the stages of development in the foregoing description. It is, however, necessary to the production of a product of optimum quality .that strain be eliminated at all stages of the manufacture.

It will also be obvious that the apparatus illustrated may be considerably modiiied as to the construction of the various elements hereinbefore referred to. I, accordingly, do not wish to be understood as limiting myself to the particular method or arrangement herein described except as hereinafter claimed.

I claim:

1. In a method of continuously making vulcanized fiber wherein a plurality of cellulose webs are passed through a peptonizing bath and then formed Ainto a continuous laminated strip while still in a comparatively unweakened condition, the steps which comprise collecting and bodily supporting the formed laminated strip in a slack untensioned state While conveying the same through a course of predetermined length in which peptonization actively occurs to render the strip a substantially gel-like ma'ssI of interlaced micelle structures materially weaker than the normal wet strength of the webs, and then passing the thus peptized strip in a slack substantially oating state through leaching and puring baths to wash the peptonizing bath from the strip and substantially strengthen said strip, the supported conveyance and floating passage ofthe strip in a slack untensioned condition through the active peptonization, leaching and puring stages serving to prevent. disturbance of the cellulose micella orientation'in said strip due to longitudinal strain and thereby maintain the interlaced relationship of the micelle structures therein.

2. In the method of continuously making vulcanized ber wherein a plurality of cellulose webs are passed through a peptonizing bath and then formed into a continuous laminated strip i while still in a comparatively unweakened condition, the steps which comprise collecting and bodily supporting the Iformed laminated strip `in a slackuntensioned state while conveying the same through a course of predetermined length in which peptonization actively occurs to render the strip a substantially gel-like mass of interlaced micelle structures materially weaker than v the normal wet strength of the webs, then passold and new methods .there is no substantial varing the thus peptized strip in a slack substantially floating state through leaching and puring baths to wash the peptonizing :bath from the strip and substantially strengthen said strip, the supported conveyance and floating passage of the strip in a slack untensioned condition through the active peptonization, leaching and ptring stages serving to prevent disturbance ofthe cellulose micella orientation in said strip due to longitudinal strain and thereby maintain the interlaced relationship of the micelle structures therein, and drying the strip while supporting the same in asubstantially untensioned state and compensating for shrinkage of the web against its support to eliminate longitudinal tension on the strip and thereby prevent distortion and lengthwise stretching of the interlaced micelle structures therein during drying.

3. In themethod of continuously making vu1. canized fiber wherein a plurality of cellulose webs are passed through a peptonizing bath and then formed into a continuous laminated strip while still in a comparatively unweakened condition, the steps which comprise collecting and bodily supporting the formedvlaminated strip in a slack untensioned state while positively conveying the same at the'rate of formation thereof through a course of predetermined length inA which peptonization actively .occurs to render the stripa substantially gel-like mass of interlaced micelle structures materially weaker than the normal wet strength of the webs, and then passing the thus peptized strip in a slack substantially floating state through leaching and puring baths to Wash the peptonizing bath from. the strip and substantially strengthen said strip, the supported conveyance and oating passage of the strip in a slack untensioned condition through the active peptonization, leaching and puring stages serving to prevent disturbance of the cellulose micella orientation in said stirp due to longitudinal strain and thereby maintain the interlaced relationship of the micelle structures therein.

4. In the method of continuously making vulcanized fiber wherein a plurality of cellulose Webs are passed through a peptonizing bath and then formed into a continuous laminated strip while still in a comparatively unweakened condition, the steps which comprise collecting and bodily supporting the formed laminated strip in a slack untensioned state while positively conveying the same at the rate of formation thereof through a course of predetermined length in which peptonization actively occurs to render the strip a. substantially gel-like mass of interlaced micelle structures materially weaker than the normal wet strength of the webs, then passing the thus peptized strip in a slack substantially oatng state through leaching and puring baths to wash the peptonizing bath from the strip and substantially strengthen said strip, the supported conveyance and oating passage of the strip in a slack untensioned condition through the active peptonization, leaching and puring stages serving to prevent disturbance of the cellulose micella orientation in said strip due to longitudinal strain and thereby maintain the interlaced relationship of the micelle structures i therein, and drying the strip while supporting the same in a substantially untensioned state and compensating for shrinkage of the web against its support to eliminate lengthwise tension on the strip and thereby prevent distortion and lengthwise stretching of the interlaced micelle structures thereinduring drying.

5. In the method of continuously making vulcanized fiber wherein a cellulose strip is passed through a peptonizing .bath and then removed therefrom while still in a comparatively unweakened condition, the steps which comprise collecting and bodily supporting the strip in a slack untensioned state while conveying the same through a course of predetermined length in which peptonization actively occurs to render the strip a substantially gel-like mass of interlaced micelle structures materially weaker than the normal wet strength of the strip and then passing the thus peptized strip in a slack substantially oating state through leaching and puring baths to wash the peptonizing bath from the strip and substantially strengthen said strip, the supported conveyance and oating passage of the strip in a slack untensioned condition through the active peptonization, leaching and puring stages serving to prevent disturbance of the celluloseimicella orientation in said strip due to longitudinal strain and thereby maintain the interlaced relationship of the micelle structures therein.

6.V In the method of continuously making vulcanized fiber wherein a cellulose strip is passed through a peptonizing bath and then removed therefrom While'still in a comparatively unweakened condition, the steps which comprise collecting and bodily supporting the strip in a slack untensioned state while conveying the same through a course of predetermined length in which peptonization activelyoccurs to render the strip a substantially gel-like mass of interlaced -micelle structures materially weaker than the normal wet strength of the strip, then passing the thus peptized strip in a slack substantially oatingstate through leaching and puring baths to wash the peptonizing bath from the strip and substantially strengthen said strip, the supporting conveyance and floating passage of the strip in a slack untensioned condition through the active peptonization, leaching and puring stagesservlng to prevent disturbancel of the cellulose micella orientation in said strip due to longitudinal strain and thereby maintain the interlaced relationship of the micelle structures therein, and drying the strip while supporting the same in a substantially untensioned state and compensating for shrinkage of the web against its support to eliminate longitudinal tension on the strip and thereby prevent distortion `and .lengthwise stretching of the interlaced micelle structures therein during drying.

GUSTAVE E. LANDT. l 

